Method for preparing tetrakis (pentafluorophenyl) borate derivatives

ABSTRACT

The invention concerns a novel method for preparing tetrakis(pentafluorophenyl)borate derivatives of general formula MB(C 6 F 5 ) 4 , M being selected among Na + , Li + , or K + , wherein: (a) a C 6 F 5 X solution, X being selected among H, Cl, Br or I, in anhydrous butylic ether is contacted with an alkyllithium, the mol ratio of C 6 F 5 X/alkyllithium being 1 to 1.1, and the alkyl radical, linear or branched comprising 1 to 10 carbon atoms; (b) the resulting product is contacted with previously non-dissolved BR 3 , R, identical or different being selected among a chlorine atom, a fluorine atom, a bromine atom, an alkoxy radical comprising between 1 and 4 carbon atoms.

This application is an application under 35 U.S.C. Section 371 ofInternational Application Number PCT/FR99/01910 filed on Aug. 02, 1999.

A subject matter of the present invention is a novel process for thepreparation of tetrakis(pentafluorophenyl)borate derivatives.

The borate derivatives obtained according to the invention are productsof use as intermediates in the preparation of catalysts for crosslinkingand/or for polymerizing by the thermal route, by the photochemical routeand/or under an electron beam.

These intermediates can also be used to prepare catalysts ofZiegler-Natta type for the polymerization of olefins, such as thosedisclosed, for example, in the documents WO 9412547 and EP-A-277 004.

In recent years, numerous documents have been published relating to theuse of the polymerization catalysts obtained fromtetrakis(pentafluorophenyl)borate derivatives. Mention will inparticular be made, by way of examples, of the Patents EP 562 897 and EP56 922 from Rhodia Chimie.

Other documents relate to the preparation oftetrakis(pentafluorophenyl)borate derivatives. For example, the documentEP 604 961 discloses access to the borates MB(C₆F⁵)₄ by the magnesiumderivative route and the document EP 608 563 discloses access to theproduct LiB(C₆F₅)₄ from pentafluorobenzene in solution in ethyl ether.

However, the processes, in particular industrial processes, disclosed inthe literature are not satisfactory. In particular, the use of anorganomagnesium derivative does not allow a high yield to be obtainedfrom the reaction for the conversion of BR₃, more specifically BCl₃, toB(C₆F₅)₄ ⁻. Likewise, the use of solvents, such as ethyl ether orisopropyl ether, does not allow the industrial processes to be optimizedin terms of reaction time and of yield of final product. By way ofexample, the use of boron trichloride in the gaseous form cannot beenvisaged with ethyl ether or isopropyl ether. This is because the BCl₃forms, with these ethers, relatively stable complexes which do not reactto any extent with the compound LiC₆F₅.

A subject matter of the present invention is a novel optimized processfor the preparation of tetrakis(pentafluorophenyl)borate derivativeswhich makes it possible to landings the abovementioned disadvantages.

Among the numerous advantages of this novel process, the purity of thetetrakis(pentafluorobenzene)borate derivatives and in particular ofpotassium tetrakis(pentafluorobenzene)borate is improved. In addition,the novel process generates only a very small amount of B(C₆F₅)₃byproduct.

Thus, a novel process for the preparation oftetrakis(pentafluorophenyl)borate of general formula MB(C₆F₅)₄ (I), Mbeing chosen from Na⁺, Li⁺ or K⁺, has thus now been developed, in whichprocess:

(a) a solution of C₆F₅X, X being chosen from H, Cl, Br and I, inanhydrous butyl ether is brought into contact with an alkyllithium, theC₆F₅X/alkyllithium molar ratio being between 1 and 1.1 and the alkylradical being chosen from linear or branched radicals comprising from 1to 10 carbon atoms and preferably a hexyl radical;

(b) the resulting product is brought into contact with BR₃ (II),undissolved beforehand before its use, R, which is identical ordifferent, being chosen from a chlorine atom, a fluorine atom, a bromineatom and an alkoxy radical comprising from 1 to 4 carbon atoms.

BR₃ used thus makes it possible to dispense with a conditioning stagebefore its introduction. This direct use of BR₃ greatly improves thereaction rate within the mixture (direct contacting).

Furthermore, the choice of anhydrous butyl ether as solvent and of BR₃makes it possible to avoid the formation of complexes which may bestable and harmful to the reactivity of the products employed in thepreparation process.

According to a first specific form of the invention, BR₃ isadvantageously introduced into the reaction mixture in the gaseous form.

According to a second specific form of the invention, BR₃ is borontrichloride.

Mention will be made, as examples of other BR₃ (II) products, ofBF₃.OEt₂, B(OMe)₃, BBr₃, and the like.

As an example of an industrial preparation process according to theinvention, the stages below are followed for the preparation ofpotassium tetrakis(pentafluorophenyl)borate:

(a) the anhydrous butyl ether and the pentafluorobenzene are introducedinto the reactor and are then mixed with stirring while cooling to atemperature of approximately −70° C.,

(b) a solution of alkyllithium and preferably of hexyllithium is runinto the reaction mixture at a controlled rate,

(c) undissolved BR₃, preferably boron trichloride, is then added to thereaction mixture and the mixture is allowed to rise to a temperature inthe region of 0° C.,

(d) an aqueous potassium chloride solution is then introduced, themixture subsequently being stirred at ambient temperature,

(e) after separating by settling, the aqueous phase is withdrawn and apotassium chloride solution is added before distilling under a reducedpressure, preferably of less than 500 mbar,

(f) after filtering and optionally washing, thetetrakis(pentafluorophenyl)borate derivative of general formulaKB(C₆F₅)₄ is recovered.

EXAMPLES

The following examples are given by way of illustration. They make itpossible in particular to achieve a better understanding of theinvention and to emphasize some of the advantages and to glimpse someone of the alternative implementational forms.

The Preparation Examples 1 and 2 are preparation processes according tothe invention and Example 3 is a preparation process given by way ofcomparison.

Example 1

The following:

200 ml of anhydrous butyl ether (Aldrich),

36 g of pentafluorobenzene (Fluorose), are charged to a 0.7 l jacketedhomothetic reactor equipped with a Rushes turbine and carefully inertwith argon.

The mixture is stirred and cooled to a temperature of −70° C. bycirculating acetone cooled with dry ice.

56.8 g of a 33% solution of hexyllithium in hexane (Chemetall) are thenrun in via a dropping funnel. The time for the introduction is 20 minand the temperature of the reaction mass changes between −70° C. and−63° C.

This mixture is stirred for 20 min. The temperature falls back to −70°C. 49.5 ml of a 1 M solution of boron trichloride in heptane (Aldrich)are added dropwise to the reaction mass. The mixture is subsequentlyleft to stir for 10 min and then the circulating liquid coolant is cutoff.

The temperature of the mixture rises to approximately 0.5° C., at whichtemperature 250 ml of a 25% solution of KCl in water are added. Thetemperature changes from 0.5° C. to 17° C. during the addition. Thestirring rate is increased. The mixture is stirred for 2 h at ambienttemperature and then stirring is halted. The reaction mass is separatedby settling. The aqueous phase (246 ml) is withdrawn.

The organic phase remaining in the reactor is stirred and the droppingfunnel is replaced with a Vigreux return column, a separator and a 500ml collecting flask. 250 ml of the 25% aqueous KCl solution are charged.

The jacket of the reactor is heated to a temperature of 85° C. and thepressure inside the apparatus is reduced to approximately 200 mbar. Theorganic solvents are distilled off without exceeding a temperature of76° C. in the reaction mass. After having distilled off 275 ml ofreaction mixture (including 60 ml of water), the appearance of a whiteprecipitate of KB(C₆F₅)₄ is observed.

The entire setup is brought back to atmospheric pressure. 60 ml of waterand 50 ml of toluene are added to the reaction mass.

After having set the pressure in the apparatus at approximately 200mbar, distillation is continued.

45 ml of distillate are recovered. The pressure in the apparatus isbrought back to atmospheric pressure and then the reaction mass iscooled to a temperature of 35° C.

The potassium tetrakis(pentafluorophenyl)borate precipitates. It isrecovered by filtering through a No. 3 sintered glass funnel. Washingwith 100 ml of rinsing water from the reactor is carried out. The whitesolid obtained is dried for 16 h at a temperature of 50° C. under avacuum of 20 mbar.

34.4 g of potassium tetrakis(pentafluorophenyl)borate are recovered,i.e.:

a yield of 96.8% with respect to the BCl₃ charged,

a yield of 89.4% with respect to the pentafluorobenzene charged.

The analytical characteristics of the product obtained are found inTable 1.

Example 2

The following:

200 ml of anhydrous butyl ether (Aldrich),

36 g of pentafluorobenzene (Fluorochem), are charged to a 0.7 l jacketedhomothetic reactor equipped with a Rushton turbine and carefully inertedwith argon.

The mixture is stirred and cooled to a temperature of −70° C. bycirculating acetone cooled with dry ice.

56.8 g of a 33% solution of hexyllithium in hexane (Chemetall) are thenrun in via a dropping funnel. The time for the introduction is 20 minand the temperature of the reaction mass changes between −70° C. and−63° C.

This mixture is stirred for 20 min. The temperature falls back to −70°C. 5.8 g of gaseous boron trichloride are introduced over 5 min using adip pipe. The mixture is subsequently left to stir for 10 min and thenthe circulating liquid coolant is cut off.

The temperature of the reaction mixture rises to a temperature ofapproximately 0.5° C., at which temperature 250 ml of a 25% solution ofKCl in water are added.

The temperature changes from 0.5° C. to 17° C. during the addition. Thestirring rate is increased. The mixture is stirred for 2 h at ambienttemperature and then stirring is halted. The reaction mass is separatedby settling. The aqueous phase (246 ml) is withdrawn.

The organic phase remaining in the reactor is stirred and the droppingfunnel is replaced with a Vigreux return column, a separator and a 500ml collecting flask.

250 ml of the 25% aqueous KCl solution are charged.

The jacket of the reactor is heated to a temperature of 85° C. and thepressure inside the apparatus is reduced to 200 mbar. The organicsolvents are distilled off without exceeding a temperature of 76° C. inthe reaction mass. After having distilled off 275 ml of reaction mixture(including 60 ml of water), the appearance of a white precipitate ofKB(C₆F₅)₄ is observed.

The entire setup is brought back to atmospheric pressure. 60 ml of waterand 50 ml of toluene are added to the reaction mass.

After having set the pressure in the apparatus at 200 mbar, distillationis continued.

45 ml of distillate are recovered. The pressure in the apparatus isbrought back to atmospheric pressure and then the reaction mass iscooled to a temperature of 35° C.

The potassium tetrakis(pentafluorophenyl)borate precipitates. It isrecovered by filtering through a No. 3 sintered glass funnel. Washingwith 100 ml of rinsing water from the reactor is carried out. The whitesolid obtained is dried for 16 h at a temperature of 50° C. under avacuum of 20 mbar.

33.22 g of potassium tetrakis(pentafluorophenyl)borate are recovered,i.e.:

a yield of 93.5% with respect to the BCl₃ charged,

a yield of 86.4% with respect to the pentafluorobenzene charged.

The analytical characteristics of the product obtained are found inTable 1.

Example 3

The following:

200 ml of anhydrous isopropyl ether (Aldrich),

36 g of pentafluorobenzene (Fluorochem), are charged to a 0.7 l jacketedhomothetic reactor equipped with a Rushton turbine and carefully inertedwith argon.

The mixture is stirred and cooled to a temperature of −70° C. bycirculating acetone cooled with dry ice. 56.8 g of a 33% solution ofhexyllithium in hexane (Chemetall) are then run in via a droppingfunnel. The time for the introduction is 20 min and the temperature ofthe reaction mass changes between −70° C. and −63° C.

This mixture is stirred for 20 min. The temperature falls back to −70°C. 47.3 ml of a 1 M solution of boron trichloride in heptane (Aldrich)are added dropwise to the reaction mass. The mixture is subsequentlyleft to stir for 10 min and then the circulating liquid coolant is cutoff. The temperature of the mixture rises to approximately 0.5° C., atwhich temperature 250 ml of a 25% solution of KCl in water are added.The temperature changes from 0.5° C. to 17° C. during the addition. Thestirring rate is increased. The mixture is stirred for 2 h at ambienttemperature and then stirring is halted.

The reaction mass is separated by settling. The aqueous phase (246 ml)is withdrawn.

The organic phase remaining in the reactor is stirred and the droppingfunnel is replaced with a Vigreux return column, a separator and a 500ml collecting flask.

250 ml of the 25% aqueous KCl solution are charged.

The jacket of the reactor is heated to a temperature of 85° C. and thepressure inside the apparatus is reduced to approximately 200 mbar. Theorganic solvents are distilled off without exceeding a temperature of76° C. in the reaction mass. After having distilled off 275 ml ofreaction mixture (including 60 ml of water), the appearance of a whiteprecipitate of KB (C₆F₅)₄ is observed.

The entire setup is brought back to atmospheric pressure. 60 ml of waterand 50 ml of toluene are added to the reaction mass.

After having set the pressure in the apparatus at 200 mbar, distillationis continued.

45 ml of distillate are recovered. The pressure in the apparatus isbrought back to atmospheric pressure and then the reaction mass iscooled to a temperature of 35° C.

The potassium tetrakis(pentafluorophenyl)borate precipitates. It isrecovered by filtering through a No. 3 sintered glass funnel. Washingwith 100 ml of rinsing water from the reactor is carried out. Twowashing operations with 30 ml of toluene are subsequently carried out.The white solid obtained is dried for 16 h at a temperature of 50° C.under a vacuum of 20 mbar.

30.1 g of potassium tetrakis(pentafluorophenyl)borate are recovered,i.e.:

a yield of 88.6% with respect to the BCl₃ charged,

a yield of 80.8% with respect to the pentafluorobenzene charged.

The analytical characteristics of the product obtained are found inTable 1.

Example 4

A 4000 ml four-necked round-bottomed flask equipped with a mechanicalstirrer, a water-cooled condenser, a thermometer and a dropping funnelis used. The setup is dried beforehand under an argon atmosphere andthen anhydrous heptane (1600 ml) and bromopentafluorobenzene (151.7 g,0.614 mol) are charged.

The combined mixture is stirred and is cooled to −75° C. using anacetone/dry ice bath. Butyllithium (1.6 M solution in hexane, 373 ml) ischarged to the dropping funnel and is added dropwise over 50 minutes.

The mixture is subsequently left to stir for hours at a temperature of−78° C. Boron trichloride (1 M solution in hexane, 149 ml) is charged tothe non-cooled dropping funnel and is added over thirty minutes. Thecooling bath is removed and the reaction mixture is allowed to return toambient temperature.

The reaction mixture is subsequently left to stir for 12 hours. Asaturated-aqueous KCl solution (180 g in 750 ml of water) is addeddropwise and then the mixture is left to stir for two hours.

The reaction mixture is filtered and the filtrate is washed with asaturated KCl solution and is then dried at a temperature of 40° C.under a vacuum of 1 mm Hg.

The potassium tetrakis(pentafluorophenyl)borate is recovered in the formof a white powder.

The analytical characteristics of the product obtained are found inTable 1.

TABLE 1 Example Example Example Example 1 2 3 4 Yield/BCl3 (%) 96.8 93.588.6 92 Yield/C₆H₅H (%) 89.4 86.4 80.8 / NMR analysis (molar %)KB(C₆F₅)₄ >99 98 96 95 KB(C₆F₅)₃OH 0 2 1  3 HPLC analysis (wgt %)KB(C₆F₅)₄ 94 96 95 / KB(C₆F₅)₃OH 0.5 0.5 0.8 / H₂O (wgt %) 2.71 2.522.50 / Cl (wgt %) 0.05 0.2 0.1 /

What is claimed is:
 1. A process for the preparation of potassiumtetrakis(pentafluorobenzene)borate in a reactor, comprising thefollowing steps: (a) adding anhydrous butyl ether and pentafluorobenzeneinto the reactor to obtain a reaction mixture, and, then, mixing withstirring the reaction mixture while cooling to a temperature of about−70° C., to obtain a step (a) reaction mixture, (b) running a solutionof alkyllithium into the step (a) reaction mixture at a controlled rate,to obtained a step (b) reaction mixture, (c) adding BR₃, undissolvedbeforehand, to the step (b) reaction mixture, wherein the R groups,identical or different, are a chlorine atom, a fluorine atom, a bromineatom or an alkoxy radical comprising between 1 and 4 carbon atoms, andrising the temperature to about 0° C., to obtain a step (c) reactionmixture, (d) adding an aqueous potassium chloride solution to the step(c) reaction mixture, and then stirring at ambient temperature, toobtain a step (d) reaction mixture, (e) settling the step (d) reactionmixture to obtain an aqueous phase and an organic phase, withdrawingsaid aqueous phase, adding a potassium chloride solution to the organicphase and, then, distilling the organic phase under a reduced pressure,to obtain potassium tetrakis(pentafluorophenyl)borate, and (f)recovering after filtering the potassiumtetrakis(pentafluorophenyl)borate obtained in step (e).
 2. The processas claimed in claim 1, wherein the alkyllithium is hexyllithium.
 3. Theprocess as claimed in claim 1, wherein BR₃ is boron trichloride.